I. Field of the Invention
This invention relates generally to apparatus for industrial pre-cleaning of machine parts prior to painting or powder coating of such parts, and more particularly to a multi-stage, in-line washer whereby parts to be cleaned are subjected to a pressurized spray at elevated temperatures of chemical cleaning solutions for predetermined time periods determined by the number of stages employed.
II. Discussion of the Prior Art
As explained in the Pascaru U.S. Pat. No. 5,257,739, machined parts must be chemically cleaned to remove oils and other residues therefrom before painting or powder coating operations can be performed on these parts. Spraying equipment used to clean, rinse and otherwise treat articles of manufacture take place in a confined area, such as a spray or washer booth, in which various liquids are piped under pressure through headers into a plurality of vertical pipes, called risers, that connect to the headers and then out through nozzles attached to the risers and which are adapted to forcefully spray work pieces as they pass through the washer booth being transported by an overhead conveyor or other suitable transport mechanism.
As further explained, prior art washer booths are customarily made of steel and are equipped with a pair of header pipes that are spaced apart and that run parallel and longitudinal to the floor or ceiling of the washer booth. Industrial liquids are stored in a tank beneath the washer booth floor and are pumped through suitable plumbing to the headers. A bank of plastic or steel risers is connected to each header and extends upward or downward along an adjacent wall of the washer booth depending on the header's placement. Parts to be treated may be carried through the booth and exposed to chemical spray by a suitable conveyor.
Pretreatment systems have four major process requirements needed to affect suitable parts cleaning. They are:                Temperature of the bath;        Concentration of the chemistry in the bath;        Pressure of the liquid spray on the part (impingement);        Time in each wash stage.        
The concentration, pressure and temperature are capable of adjustment once the washer is built, but after a washer has been built; the exposure time is fixed, based on the length dimension of the washer and each of its stages.
For example, assume a company has designed to run a conveyor of the parts to be cleaned at 4 feet per minute and that three process stages are required. Three process stages typically require two drip zones, one entrance and one exit vestibule with a 1 minute soak time required in each stage. Under these assumptions, a wash booth would have to be 28 feet in length. Over time, should the company decide to increase the conveyor speed to add throughput, it would have to sacrifice soak time or, alternatively, add length to the washer, usually at considerable expense. Also, if the company needs to add another stage to improve its process or possibly add another type of process, it will not be able to do that without substantial added cost. In the case of the prior art, it is a major project to add length to a washer or to shorten it.
Existing washers of which we are aware typically occupy a significant amount of factory floor space and are inefficient in terms of energy needed to pump and heat the liquid cleaning agents.
Those skilled in the art, then, can appreciate that a need exists for an in-line pretreatment system that is modular in design, allowing stages to be easily added or removed based upon customer requirements.
Another problem with prior art parts washer booths is that they do not permit easy access to the piping system comprising the nozzles, risers and headers contained within the booth so that adjustments may be made to the direction and spray pattern employed. Thus, a need exists for an in-line pretreatment system that allows easy access to interior components for cleaning, adjustment repair and replacement.
Another drawback of prior art washers is that they need some type of filtration system in the first wash stage to help keep the bath clean so as to offer an extended bath life. The filtration systems commonly employed require an additional pump and bag filtration system typically placed adjacent to the washer. Such filtration systems therefore require additional energy and floor space. A need therefore exists for a more compact and energy efficient way for filtering the wash chemicals.
It is therefore a principal object of the present invention to provide an in-line pretreatment system for washing machine parts that solves the aforementioned problems attendant in known prior art systems by providing a modular configuration of different length stages that can be concatenated to vary the time of exposure and the types of chemicals needed for the cleaning process at hand. The modules have been specifically designed to provide greater flexibility and ease of access to interior components while also reducing the overall footprint and energy consumption needed to operate the system.